In recent years there has been an explosive increase in our knowledge of the presence and function of neuronally produced peptides in animals. Immunohistochemical studies have demonstrated their ubiquity, and physiological studies have implicated them as regulators in such interesting processes as the perception of pain, appetite, thirst, sleep, and memory. The proposed work is intended to define specific biochemical mechanisms that regulate the process of neurosecretion of that message into high molecular weight precursor, its processing into biologically active secretory products, its packaging into neurosecretory granules, and its transport to distal storage and release sites. Specifically stimulated release of a neuropeptide with the transcription of the gene encoding it, the translation of that message into high molecular weight precursor, its processing into biologically active secretory storage and release sites. Specifically, this project proposes to define the nature of neurosecretory products that are apparently induced in the caudal neurosecretory complex (CNC) of the normally marine fish, Gillichthys mirabillis, when it is acclimated to fresh water. Recent evidence suggests that several known neurosecretory peptides of the CNC are induced by environmental change from seawater to fresh water as well as at least one previously unknown product. Comparison of biosynthetic states of CNC tissues under control and stimulated conditions may provide a useful 'handle' by which we can manipulate neurosecretion in this system. The CNC of this fish is particularly well suited as a model system for studies of the regulation of neurosecretion since it can be removed from the animal and maintained in a functional state for several days in organ culture. The identification of the structure of the induced molecules and the mRNAs which encode them is a necessary preliminary step in pursuit of our long term goals to study the regulation of the neurosecretory process as a whole.